GlaxoSmithKline said on Monday it had filed for U.S. approval of its new once-weekly diabetes drug albiglutide and would make a similar submission shortly in Europe as it vies for a share of a crowded market. Albiglutide belongs to the same class of injectable GLP-1 medicines as Victoza, from Novo Nordisk, and Byetta and Bydureon, from Bristol-Myers Squibb and AstraZeneca's Amylin unit. The submission by GSK, Britain's biggest drugmaker, was in line with its plan to seek regulatory approval for the new product in 2013. As a latecomer to the GLP-1 market, however, analysts believe albiglutide may struggle to generate major sales. Consensus forecasts for albiglutide currently point to modest annual sales of around $367 million by 2017, according to Thomson Reuters Pharma.